An item specifically designed to fit into the opening(s) of various items to provide mechanical protection and/or prevent the entrance of foreign matter during painting, shipping storage, or the like. It is not designed to retain fluids under pressure during equipment operation. Excludes PLUG (as modified) and STOPPER, BOTTLE. For items designed to fit into or over the opening(s) of various items, see CAP-PLUG, PROTECTIVE, DUST AND MOISTURE SEAL.